In a laboratory at Purdue University's School of Veterinary Medicine, Dr. Suresh Mittal and his research assistants are working against time to develop a vaccine for the H1N1 influenza A virus. Purdue is one of eight to 10 organizations to which the Centers for Disease Control has sent H1N1 genetic material for developing a vaccine, said CDC spokesman Erik Friedly.

“We are using two pieces of DNA fragment, one from the H1N1 and one from a common cold virus, the adenovirus,” Mittal said. The adenovirus carries the H1N1 gene but does not cause disease in humans and does not replicate.

The DNA from both viruses is purified. Enzymes are used to tie the two viruses together, “and we create a new virus inside the cells using the purified DNA complement,” said Mittal.

If World Health Organization leaders, meeting this week in Geneva, Switzerland, decide full-scale manufacturing of H1N1 vaccine should begin, the coming flu season could mean two flu shots instead of one.

Mittal used the same process he's using for H1N1 to develop a vaccine for the H5N1 strain of avian flu that caused concern in recent years. Purdue offered the H5N1 vaccine technology to a commercial vaccine manufacturer. Mittal said he cannot name the company because of his role as an academic researcher. The company has been testing the H5N1 vaccine on humans and found it to be safe and effective, he said.

Mittal says his H1N1 vaccine should be ready for testing in mice in about two weeks. Then it will be turned over to the commercial company. The vaccine is grown in tissue, or cellular material, not in chicken eggs, which are used in growing most seasonal flu vaccines.

“Our system is different. The (commercial) company has used this for gene therapy, for cancer treatment,” Mittal said. “They have developed the capability of growing and purifying the virus. The efficacy and safety has already been done,” although testing of the H1N1 vaccine in humans will still be required.

The WHO's pandemic alert system is based on how widespread a disease is, not its severity. As H1N1 continues to spread, it appears inevitable that the pandemic level will move to 6, the highest level. Yet some WHO members are asking for severity to be considered to avoid panic that would further devastate the world economy, force border closures and require other politically charged decisions.

Although the global H1N1 death toll has climbed to nearly 80 among 9,000 confirmed cases in 40 countries, experts say victims had other health problems.

Mittal said H1N1 and H5N1 severity levels differ in part because of how they affect the respiratory system, noting, “H5N1 bird flu grows deep in the lungs.” In healthy individuals, it appears to set off a massive inflammatory response called a “cytokine storm,” causing a blockage of the airway, yet the disease is more difficult to spread.

“The H1N1 virus grows in the upper-respiratory tract,” he said. A slight cough or sneeze makes it easily transmissible but not so devastating for healthy individuals.

Because seasonal flu viruses change frequently, developing a vaccine is a moving target from year to year. On the other hand, H1N1 has not shown much change, Dr. Carolyn Bridges said in a recent audio briefing with journalists. She is associate director of epidemiologic science for the CDC's Influenza Division. Seasonal flu can have 12 to 19 genetic variations, whereas the H1N1 has shown up to five so far.

But the looming question is, will H1N1 remain stable so the vaccine Mittal and others are working on can be made in time, or will it change into a more virulent strain?

“I think it will be a guess,” Mittal said. “But we have to get prepared for the incoming flu season. It's already too late to add another component,” Mittal said of vaccine manufacturers trying to combine the H1N1 vaccine with the seasonal flu vaccine.

If the WHO this week recommends use of H1N1 vaccine, scientists will step up efforts to look at how the seasonal flu and H1N1 might be combined. But Mittal said, “It's very conceivable that we could have two flu vaccines for next year.”